Method of producing heat-resistant crimped yarn

ABSTRACT

The present invention relates to a method for producing a heat-resistant crimped yarn comprising: twisting yarn of a heat-resistant high functional fiber; twist-setting this twisted yarn by heat treatment; and untwisting this twist-set yarn, wherein a snarl value of the twist-set yarn is not more than 6.5.

TECHNICAL FIELD

The present invention relates to a method for producing a heat-resistantcrimped yarn comprising heat-resistant high functional fibers such asaramid fibers or the like. More precisely, the invention relates to amethod for producing a heat-resistant crimped yarn, which exhibits agood elongation percentage during stretching and a good appearance so asto be able to provide woven or knitted fabric with elasticity andbulkiness. Concretely, the invention relates to a method, whichcomprises heat-setting twisted yarn of a heat-resistant high functionalfiber to produce a heat-set yarn of which a snarl value is not more than6.5, and untwisting the heat-set yarn.

The present invention also relates to a method useful for producing aheat-resistant crimped yarn on a commercial basis, which ischaracterized by treatment of twisted yarn with steam having hightemperature and high pressure or water having high temperature and highpressure, preferably under decompression, following a specific twistingprocess of a yarn as mentioned hereinabove.

Moreover, the present invention relates to a bobbin suitable forproducing a heat-resistant crimped yarn made of fibers such as aramidfiber or the like on a commercial basis.

BACKGROUND ART

General thermoplastic synthetic fibers such as nylon or polyester fibermelt at about 250° C. However, heat-resistant high functional fiberssuch as aramid fiber, wholly aromatic polyester fiber andpolyparaphenylene-benzobisoxazole fiber do not melt at 250° C., and adecomposition temperature of these fibers is about 500° C. A limitedoxygen index of non-heat-resistant general fibers such as nylon orpolyester fiber is about 20, and these fibers burn well in air. However,a limited oxygen index of heat-resistant high functional fibers such asthose mentioned above is at least about 25, and these fibers may burn inair when they are brought close to a heat source of flame, but could notcontinue to burn if they are moved away from the flame. To that effect,a heat-resistant high functional fiber has excellent heat resistance andflame retardancy. For example, as a kind of heat-resistant highfunctional fiber, an aramid fiber is favorable to clothes for use at ahigh risk of exposure to flame and high temperature, for example,fireman's clothes, racer's clothes, steelworker's clothes, welder'sclothes, and the like. Above all, a para-aramid fiber having advantagesof heat resistance and high tenacity is much used for sportsman'sclothes, working clothes and others that are required to have high tearstrength and heat resistance. In addition, as it is hardly cut withedged tools, this fiber is also used for working gloves. On the otherhand, a meta-aramid fiber is not only resistant to heat, but also hasgood weather resistance and chemical resistance, and it is used forfireman's clothes, heat-insulating filters, and electric insulators, andthe like.

Heretofore, when a heat-resistant high functional fiber is formed intotextile goods such as clothes, it is used merely in a form ofnon-crimped continuous filament yarn or spun yarn. However, when suchnon-crimped continuous filament yarn or spun yarn is woven or knittedinto fabrics, and from them formed into clothes such as fireman'sclothes, racer's clothes and working clothes, these resulting clothesare poorly elastic as the yarn itself is not elastic. As a result, whenthe clothes are worn, they are unsuitable to exercises and workingactivities. In particular, working gloves made of a non-crimpedcontinuous filament yarn and a spun yarn are unsuitable to use inindustrial fields of airplane and information instrument in whichprecision parts are handled, as they are unsuitable to exercises andworking activities. Using the gloves mentioned hereinabove in thoseindustrial fields often results in a lowering of productivity.Accordingly, an improvement of such a sort of disadvantages ofheat-resistant textile goods that exhibit uncomfortable feeling whenworn for a working activity is desired.

It is easy to produce a highly crimped filament yarn from generalthermoplastic synthetic fibers such as nylon or polyester fiber by usingheat-set. For example, known is a false-twisting method for crimping inwhich a thermoplastic synthetic fiber is twisted, heat-set and cooled.Also known is a stuffing box method for crimping in which athermoplastic synthetic fiber is forcedly pushed into a rectangularspace, and then heat-set.

On the other hand, it is impossible or very difficult to produce acrimped filament yarn of heat-resistant high functional fiber under thesame process conditions and procedures as in the false-twisting methodor the stuffing box method described above, since this heat-resistanthigh functional fiber is non-thermoplastic and therefore poorlyheat-set. A crimping method which is suitable to a heat-resistant highfunctional fiber has not been established yet, so a heat-resistant highfunctional fiber has been used only in a form of non-crimped continuousfilament yarn or spun yarn.

However, many studies and proposals have been made, relating to aheat-resistant high functional crimped yarn and to a method for crimpingheat-resistant high functional fibers. Concretely, known are a methodfor producing a heat-resistant crimped fiber from heat-resistant fiberssuch as wholly aromatic polyamide fiber by selecting spinningconditions, without using a special crimping method and device (JapanesePatent Laid-Open No. 19818/1973), a non-heat stuffing box method inwhich an optical anisotropic dope such as para-wholly aromatic polyamideor the like is crimped in a stuffing box at room temperature and driedunder a state of relaxation after performing a wet spinning method bydry-jet(Japanese Patent Laid-Open No. 114923/1978), a stuffing boxmethod in which a high-elastic fiber such as a para-aramid fiber iscrimped, and mixed with a low-elastic fiber (Japanese Patent Laid-OpenNo. 192839/1989), a method in which an aramid self-crimping filamentyarn is produced by wet-and-dry spinning an optical anisotropic dopeconsisting of aramid and sulfuric acid under specific conditions(Japanese Patent Laid-Open No. 27117/1991), and a continuous processmethod in which an aramid fiber is false-twisted and crimped by use of anon-contact heater at a temperature not lower than that at which thefiber begins to decompose but lower than a decomposition point of thefibers (for a meta-aramid fiber, the temperature is at least 390° C. butlower than 460° C.), and thereafter subjected to heat treatment underrelaxation (Japanese Patent Laid-Open No. 280120/1994). However, all ofthese known methods could still not solve outstanding technical problemswhich are how to realize easy process control, simplification ofproduction lines, high productivity, and cost reduction. At present,therefore, no one has succeeded in industrial production of aheat-resistant crimped yarn exhibiting a good elongation percentageduring stretching, wherein quality deterioration in a production processis reduced as much as possible.

SUMMARY OF THE INVENTION

In view of the problems in the related art noted above, one object ofthe present invention is to provide a method for producing a crimpedyarn comprising a heat-resistant high functional fiber, which ispractical in terms of productivity, equipment therefor and productioncosts. Another object of the invention is to provide a crimped yarnwhich is excellent in terms of a stretch modulus of elasticity,heat-resistance, tenacity and appearance, and which is produced whilereducing a quality deterioration of a constituent fiber throughperformance of a heat treatment as much as possible.

Some of the present inventors have provided a method for producing aheat-resistant crimped yarn, which comprises: twisting a heat-resistanthigh functional fiber such as an aramid fiber or the like; treating thistwisted fiber with steam having high temperature and high pressure orwith water having high temperature and high pressure (this ishereinafter referred to as treatment with steam having high temperatureand high pressure); and thereafter untwisting the twisted fiber(Japanese Application No. 361825/1999).

We, the present inventors have assiduously studied so as to attain theobjects as above, and, as a result, have found that, when a snarl valueof a heat-set yarn is not more than 6.5 in a method for producing aheat-resistant crimped yarn comprising twisting a heat-resistant highfunctional fiber, heat-setting this twisted yarn and untwisting thisheat-set yarn, twist of a product is sufficiently fixed. And we alsohave found that an elongation percentage during stretching of theheat-resistant crimped yarn produced by the above method is sufficientto provide a woven or knitted fabric with elasticity, and that idealclothes which exhibit a good elongation percentage during stretching, anexcellent heat resistance, a high tenacity, and a good appearance (forexample, fireman's clothes, racer's clothes, steel worker's clothes, andwelder's clothes, for example) can be obtained by using this fabric.

The present inventors have further studied so as to improve the abovemethod to produce a heat-resistant crimped yarn on a commercial basis.

Concretely, in producing a heat-resistant crimped yarn on a commercialbasis by using the method including treatment with steam having hightemperature and high pressure, there is a problem in that heat-settingwith steam having high temperature and high pressure is not uniformbetween a portion of the yarn at a surface of a bobbin and a portion ofthe yarn away from this surface. That is, in producing a heat-resistantcrimped yarn on a commercial basis, it is preferable so as to produceproducts more efficiently and more cost-effectively that yarn as much aspossible be subjected to treatment with steam having high temperatureand high pressure at a single time by increasing a thickness of a yarnlayer wound around a bobbin. But, in this case, steam having hightemperature and high pressure or water having high temperature and highpressure (this is hereinafter referred to simply as steam having hightemperature and high pressure) is not provided inside of a yarn cheeseor yarn corn, and an interior yarn of the yarn cheese or yarn corn (yarnwound around close to a cylinder of the bobbin) is not heat-setsufficiently. While, when steam having high temperature and highpressure is penetrated into an inner area of the yarn cheese or the yarncorn (this is hereinafter referred to as the inside) sufficiently, andwhen the inside is heat-set sufficiently by making a treatment timelonger, a surface yarn of the yarn cheese or corn (yarn wound around thebobbin far from the cylinder) deteriorates by application of heat.

We have assiduously studied so as to improve the problems as above, and,as a result, have found that uniformity in terms of heat-setting betweenthe surface and the inside by heat-setting with steam having hightemperature and high pressure can be improved by reducing pressure in anautoclave before the treatment with steam having high temperature andhigh pressure. And, we have also found unexpectedly that a necessarytime of treatment with steam having high temperature and high pressurecan be shortened by using this process. An efficiency of this productionprocess can not only be improved, but also a quality deterioration ofyarn through the treatment with steam having high temperature and highpressure can be prevented by using the process.

We have assiduously studied so as to solve the problems on a commercialbasis as mentioned above, and, as a result, have found that steam havinghigh temperature and high pressure can be provided inside efficientlyand uniformity of heat-setting between the surface and the inside can beimproved by providing a plurality of small through holes, of whichdiameter is about 2 to 9 mm on a surface of a cylinder or/and a flangeof a bobbin. Particularly, we have found that the above range of thediameter is preferable for a reason that, in case of too small ofthrough holes, steam having high temperature and high pressure is notprovided sufficiently and the through holes may be blocked, and, in caseof too large of through holes, marks are found on a heat-resistantcrimped yarn.

We have assiduously studied about a hole area rate, and, as a result,have found that the hole area rate is preferably in a range of about 1to 20%.

Having further studied, we, the present inventors have completed thepresent invention.

Specifically, the invention relates to the following:

(1) A method for producing a heat-resistant crimped yarn comprising:twisting yarn of a heat-resistant high functional fiber; twist-settingthis twisted yarn by heat treatment; and untwisting this twist-set yarn,wherein a snarl value of the twist-set yarn is not more than 6.5;

(2) The method for producing a heat-resistant crimped yarn described inabove (1), wherein an elongation percentage during stretching of aheat-resistant crimped yarn is not less than 6%;

(3) The method for producing a heat-resistant crimped yarn described inabove (1) or (2), wherein a heat treatment applied to the twisted yarnis performed by bringing the twisted yarn into contact with steam havinghigh temperature and high pressure or water having high temperature andhigh pressure;

(4) The method for producing a heat-resistant crimped yarn described inabove (3), wherein treatment of the twisted yarn with steam having hightemperature and high pressure or water having high temperature and highpressure is performed at a temperature falling between 130 and 250° C.;

(5) The method for producing a heat-resistant crimped yarn described inabove (3) or (4), which comprises making a yarn cheese or a yarn corn bywinding the twisted yarn of a heat-resistant high functional fiberaround a bobbin; loading the yarn cheese or yarn corn into an autoclave;reducing pressure in the autoclave; twist-setting the twisted yarn ofthe yarn cheese or yarn corn by bringing the twisted yarn into contactwith steam having high temperature and high pressure or water havinghigh temperature and high pressure; and untwisting this twist-set yarn;

(6) The method for producing a heat-resistant crimped yarn described inabove (5), wherein the pressure in the autoclave after reduction is from5.0×10³ to 5.0×10⁴ Pa;

(7) The method for producing a heat-resistant crimped yarn described inabove (5) or (6), wherein treatment of the twisted yarn with steamhaving high temperature and high pressure or water having hightemperature and high pressure is performed for a period of time fallingbetween 0.5 and 100 minutes;

(8) The method for producing a heat-resistant crimped yarn described inabove (5) to (7), wherein a thickness of a yarn layer of the cheese orcorn is not less than 15 mm, and a winding density thereof is not lessthan 0.5 g/cm³;

(9) The method for producing a heat-resistant crimped yarn described inabove (1) to (8), wherein a heat-resistant high functional fiber istwisted to a twist parameter K, represented by the following formula, offrom 5,000 to 11,000:K=t×D ^(1/2)wherein t indicates a count of twist (turns/m) of the fiber; and Dindicates a fineness (tex) of the fiber;

(10) The method for producing a heat-resistant crimped yarn described inabove (1) to (9), wherein a heat-resistant high functional fiber isselected from the group consisting of para-aramid fiber, meta-aramidfiber, wholly aromatic polyester fiber andpolyparaphenylene-benzobisoxazole fiber;

(11) The method for producing a heat-resistant crimped yarn described inabove (10), wherein the para-aramid fiber is apolyparaphenylene-terephthalamide fiber;

(12) A heat-resistant crimped yarn produced by the method described inany one of above (1) to (11); fabric made of the heat-resistant crimpedyarn; and clothes made of the fabric;

(13) A method for treating a yarn cheese or a yarn corn, which comprisesmaking the yarn cheese or the yarn corn by winding twisted yarn of aheat-resistant high functional fiber around a bobbin; loading the yarncheese or the yarn corn into an autoclave; reducing pressure in theautoclave loaded with the yarn cheese or the yarn corn to a pressurefalling between 5.0×10³ and 5.0×10⁴ Pa; and raising temperature in theautoclave to a temperature in the range of from 130 to 250° C. byproviding steam having high temperature and high pressure or waterhaving high temperature and high pressure into said autoclave;

(14) A heat-resistant bobbin having a plurality of small through holeson a surface of a cylinder and/or a flange of the bobbin, wherein adiameter of the small through holes is 2 to 9 mm, and a hole area ratethereof is 1 to 20%;

(15) The method for producing a heat-resistant crimped yarn described inabove (1) to (11), wherein twist-setting by heat treatment is performedby use of the yarn cheese or the yarn corn made by winding the twistedyarn of a heat-resistant high functional fiber around the heat-resistantbobbin described in above (14);

(16) The method for treating the yarn cheese or the yarn corn describedin above (13), wherein the bobbin is heat-resistant as described inabove (14);

(17) A device for producing a heat-resistant crimped yarn of aheat-resistant high functional fiber, which comprises: a device forsealing an autoclave; a device for reducing pressure in the autoclave toa pressure falling between 5.0×10³ and 5.0×10⁴ Pa; a device forsupplying steam having high temperature and high pressure or waterhaving high temperature and high pressure into the autoclave; a devicefor controlling a temperature of the steam having high temperature andhigh pressure or the water having high temperature and high pressure soas to be maintained in a range of from 130 to 250° C. for a period oftime falling between 0.5 and 100 minutes; a device for draining waterfrom the autoclave; and a device for decreasing high pressure in theautoclave to atmospheric pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows structure of a tester measuring a snarl value of heat-setyarn. In FIG. 1, symbol 1 shows hook A, symbol 2 shows hook C, symbol 3shows pin B, symbol 4 shows load, symbol 5-a shows yarn hanged on hookA, pin B and hook C, symbol 5-b shows yarn removed from pin B, andsymbol 6 shows divisions.

FIG. 2 shows a bobbin of the present invention, which has small throughholes. In FIG. 2, symbol 11 shows the bobbin of the present invention,symbol 12 shows a cylinder, symbol 13 shows a flange and symbol 14 showssmall through holes.

FIG. 3 shows an outline of an autoclave for treatment with steam havinghigh temperature and high pressure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First: a heat-resistant high functional filament yarn is twisted (thisis a primary twisting step in which a yarn is twisted in a direction ofS or Z); then this twisted yarn is wound around a heat-resistant bobbinof aluminum or the like; and then this wound twisted yarn is heat-setfor twist fixation, preferably under treatment with steam having hightemperature and high pressure or water having high temperature and highpressure for predetermined time. Next, this heat-set yarn is untwistedby secondarily twisting it opposite to a primary twisting direction(that is, in the direction of Z or S) to obtain a heat-resistant crimpedyarn.

In this method of the present invention, the filaments made of a fiberare deformed to have a spirally complicated shape after the primarytwisting step, and this shape is fixed by treatment with heat,preferably, with steam having high temperature and high pressure or withwater having high temperature and high pressure. Then, monofilamentsuntwisted by twisting in an opposite direction are released from aprimary twisting force and try to form randomly their own shapes,keeping their own memory of shapes given during the primary twistingstep, and as a result, fibers made of monofilaments obtain a form ofcrimp.

Preferably, a heat-resistant high functional fiber for use in theinvention has a limited oxygen index of not less than about 25, and athermal decomposition point measured in a differential scanningcalorimeter of not lower than about 400° C. Examples of the fiber are anaramid fiber, wholly aromatic polyester fiber (e.g., Kuraray'sCommercial product named Vectran®), polyparaphenylene-benzobisoxazolefiber (e.g., Toyobo's Commercial product named Zylon®),polybenzimidazole fiber, and the like. The aramid fiber includes ameta-aramid fiber and a para-aramid fiber. Examples of the meta-aramidfiber are meta-wholly aromatic polyamide fiber such aspolymetaphenylene-isophthalamide fiber (e.g., DuPont's Commercialproduct named Nomex®), and the like. Examples of para-aramid fibers arepara-wholly aromatic polyamide fibers such as apolyparaphenylene-terephthalamide fiber (e.g., Toray-DuPont's Commercialproduct named Kevlar®), acopolyparaphenylene-3,4′-diphenylether-terephthalamide fiber (e.g.,Teijin's Commercial product named Technora®), and the like.

Even more preferred is a para-aramid fiber, especially apolyparaphenylene-terephthalamide fiber. And more preferred is also ameta-aramid fiber.

In the present method for producing a heat-resistant crimped yarn, theyarn consisting of a heat-resistant high functional fiber is firsttwisted in a primary twisting step.

The yarn consisting of a heat-resistant high functional fiber may be inany form of either filament yarn or spun yarn. The yarn may be in theform of co-spun yarn or co-twisted yarn with two or more different kindsof the fiber. And, the yarn may be in the form of co-spun yarn orco-twisted yarn with a heat-resistant high functional fiber and otherknown fibers such as, preferably, a polyester fiber or nylon fiber. Inthis case, it is preferable that a weight percentage of a heat-resistanthigh functional fiber is not less than about 50 weight % relative toother fibers.

A filament composing a heat-resistant high functional fiber ispreferably made up of a monofilament with a very fine diameter. Forexample, a yarn, of which total fineness falls between about 22.4 to44.4 tex, fineness of a monofilament is 0.17tex and a number ofmonofilaments is 131 to 262, is more preferable.

Monofilament fineness of a heat-resistant high functional fiber used inthe invention falls between about 0.02 and 1.0 tex, but preferablybetween about 0.05 and 0.5 tex. The finer the monofilament, the softerthe yarn. Accordingly, a fine monofilament is desirable for clothes,but, on the other hand, in a process of producing a heat-resistantcrimped yarn, the finer the monofilament, the more a heat-resistantcrimped yarn fluffs and the more difficult its processing. Accordingly,in the present invention, it is preferable that the fineness of amonofilament is not less than 0.02 tex as mentioned above. The thickerthe monofilament, the more difficult it is to cut by a knife, andaccordingly, a thick monofilament is desirable for use as protectiveclothes such as working gloves. But, on the other hand, the thicker themonofilament, the stiffer it is, so softness, which is required forfinal products such as clothes, is reduced by using a thickmonofilament. Accordingly, in the present invention, it is preferablethat the fineness of a monofilament is not more than 1.0 tex asmentioned above. The total fineness of the yarn used in the invention,which is made of monofilaments, is not specifically defined so long asthe fineness of the yarn is sufficient for twisting and untwisting.However, the total fineness of the yarn falls preferably between about 5and 400 tex, because this yarn is easy to be processed.

In a twisting process, preferably, the yarn is twisted to a twistparameter K, represented by a formula K=t×D^(1/2) (wherein t indicates acount of twist (turns/m) of the fiber, and D indicates fineness (tex)thereof), of from about 5,000 to 11,000, more preferably from about6,000 to 9,000. The yarn is desired to be twisted to such a suitabledegree defined hereinabove such that the yarn is crimped appropriatelysufficient for practical use, and such that filaments of the yarn do notbreak owing to excessive twisting. The twist parameter, K, is an indexindicating a degree of twisting of the fiber irrespective of a thicknessof the fiber. The larger the value of the twist parameter, the higherthe twist degree.

As a method for twisting yarn, usable is any per-se known method. Forexample, usable is any per-se known twisting machine such as a ringtwister, a double twister, an Italy twister, and the like.

Twisting may be in either direction of Z or S.

The twisted yarn obtained above is wound around a bobbin made of aheat-resistant material such as aluminum or the like. The bobbinreferred to herein is usually an ordinary cylindrical winding corearound which yarn is wound. Cheese referred to herein is yarn wound uparound the bobbin. Especially, in a case that a diameter of each edge ofa bobbin is different and a shape of wound yarn is like corn, it isdesignated as corn or corn cheese. In a case where the twisted yarn iswound around a heat-resistant bobbin, it is unnecessary to rewind theyarn.

Preferably, a bobbin for use herein is made of heat-resistant material,because the bobbin is subjected to a heat treatment. Any per-se knownheat-resistant material, including aluminum or the like, is usableherein, preferably a bobbin made from aluminum is usable in theinvention.

Also preferably, a bobbin for use herein is worked to have a pluralityof small through holes in order that steam having high temperature andhigh pressure can easily pass through these holes during treatment withsteam having high temperature and high pressure. More preferably, thebobbin has a plurality of small through holes uniformly distributed tomeet the purpose mentioned above. The bobbin may have a plurality ofsmall through holes either in its entire surface, that is, in a surfaceof a cylinder and flange, or only in a surface of the cylinder orflange. More preferably, the bobbin has a plurality of small throughholes in the surface of cylinder.

A shape of each small through hole is not specifically defined, but isround preferably.

A diameter of each small through hole is preferably about 2 to 9 mm,more preferably about 3 to 5 mm. The diameter is preferably in thisrange to allow steam having high temperature and high pressure to enterinto an interior of the yarn cheese or yarn corn efficiently, as well asto not block a plurality of through holes, and not to leave a mark onthis yarn.

Herein, the diameter indicates a length of a longest part of the holes.For example, if the through hole is round, the diameter indicatesdiameter. If the through hole is a polygon, the diameter indicates alongest diagonal. If the through hole is an ellipse, the diameterindicates a longer axis.

In a plurality of small through holes, a hole area rate is preferablyabout 1 to 20%, more preferably about 1.5 to 10%. The hole area rate ispreferably in this range to efficiently allow steam having hightemperature and high pressure to pass into the interior of the yarncheese or yarn corn.

Herein, the hole area rate indicates a ratio of a total area of aplurality of the small through holes to total surface area of thebobbin. More concretely, the hole area rate is calculated by thefollowing formula.

The  hole  area  rate(%) = {the  total  area  of  the  small  through  holes/(the  total  surface  area  of  the  cylinder + the  total  surface  area  of  flange × 2)} × 100

A thickness of the yarn cheese or the yarn corn formed by winding thetwisted yarn around a bobbin is not less than about 15 mm; and a windingdensity thereof falls between about 0.4 to 1.0 g/cm³, more preferablybetween about 0.5 to 0.9 g/cm³, even more preferably between about 0.6to 0.9 g/cm³. It is preferable that the thickness is not less than about15 mm to be useful for production on a commercial basis. And it ispreferable that the density is in this range from a viewpoint ofconvenience for handling after treatment; that is, in order to avoidlooseness or disorder of the yarn wound on the bobbin.

Next, the yarn corn or yarn cheese is loaded into an autoclave.

The autoclave may have any per-se known structure with steam having hightemperature and high pressure being supplied thereinto. One example ofthe structure of an autoclave for use herein is equipped with a steamduct through which steam having high temperature and high pressure isfed; a water drainage valve; an exhaust valve via which the autoclave isdegassed after treatment; an inlet mouth through which the yarn cheeseor yarn corn is brought into and removed from the autoclave; and asealing device to hermetically seal a container equipped with a lidcapable of being opened and shut.

Pressure in an autoclave, in which the yarn cheese or yarn corn isloaded, is optionally reduced. Preferably, the pressure after reducingis in a range from about 5.0×10³ to 5.0×10⁴ Pa, more preferably in arange from about 5.0×10³ to 2.7×10⁴ Pa. A minimum of the pressuredepends on such a factor as the structure of the autoclave, butpreferably it is about 5.0×10³ Pa for useful production on a commercialbasis.

Air permeated through layers of wound yarn is removed by reducing thepressure mentioned above. As a result, in a next treatment process withsteam having high temperature and high pressure, steam having hightemperature and high pressure can be quickly permeated into the interiorof the yarn cheese or corn, and a uniformity of heat-setting between asurface and the interior of the yarn cheese or corn can be improved.Consequently, one preferred embodiment of the invention is a methodincluding a process of reducing the pressure.

Next, treatment with steam having high temperature and high pressure ispeformed. This treatment with steam having high temperature and highpressure may be effected in any per-se known manner. Preferably, steamhaving high temperature and high pressure is supplied to an autoclave,wherein a yarn cheese or yarn corn is loaded.

A temperature for the treatment with steam having high temperature andhigh pressure may fall between about 130 and 250° C., preferably betweenabout 130 and 220° C., more preferably between about 140 and 200° C.This temperature range is preferred in order to obtain useful crimpedyarn without a deterioration of any property of constituent fibers.

A pressure for the treatment is described. In a case where steam havinghigh temperature and high pressure for the treatment is saturated steam,its pressure shall be physicochemically defined by its temperature.Concretely, pressure of saturated steam at a lowermost temperature of130° C. is 2.70×10⁵ Pa, and is 38.97×10⁵ Pa at an uppermost temperatureof 250° C. However, steam for the treatment of the invention is notlimited to saturated steam, and its pressure may fall between about2.7×10⁵ Pa and 39.0×10⁵ Pa. Needless-to-say, steam pressure could not bemore than saturated steam pressure at the same temperature.

Especially preferably, treatment with steam having high temperature andhigh pressure is effected at a temperature falling between about 130° C.and 250° C., preferably between about 130 and 220° C., more preferablybetween about 140 and 200° C.; and under a pressure falling betweenabout 2.7×10⁵ Pa and 39.0×10 ⁵ Pa, preferably between about 2.7×10⁵ Paand 23.2×10⁵ Pa, more preferably between about 3.5×10⁵ Pa and 23.2×10⁵Pa.

In place of steam having such high temperature and high pressure, waterhaving such high temperature and high pressure can also be used herein.In this case, a water temperature may fall between about 130 and 250° C.(but preferably between about 130 and 220° C., more preferably betweenabout 140 and 220° C.); and water pressure may fall between about2.70×10⁵ Pa and 39.0×10⁵ Pa (preferably between about 2.7×10⁵ Pa and23.2×10⁵ Pa, more preferably between about 3.5×10⁵ Pa and 23.2×10⁵ Pa).For treatment with water having high temperature and high pressure,expressions “steam having high temperature and high pressure” and“steam” given hereinabove and hereinunder shall be replaced by “waterhaving high temperature and high pressure” and “water”, respectively.

A time for treatment with steam having high temperature and highpressure is not indiscriminately defined, as depending on an amount offibers of the yarn cheese or yarn corn. It is enough that apredetermined temperature is maintained for a few minutes. Preferably,the time for the treatment falls between about 2 and 100 minutes, morepreferably between about 3 and 60 minutes. In a case of production on acommercial basis, especially in a case that a process under reducedpressure mentioned above is performed, the time for treatment fallsbetween about 0.5 and 100 minutes, more preferably between about 0.5 and60 minutes, even more preferably between about 0.5 and 30 minutes. Thisdefined range of the time for the treatment is preferred for moreuniform heat-set between a surface and the interior of fibers woundaround a bobbin without any substantial deterioration of a constituentfiber.

The present invention is characterized in that a snarl value of aheat-resistant high functional twisted yarn after a heat-settingtreatment (twist set by heat treatment) is not more than 6.5. Apreferable range of the snarl value is about 6.5 to 0. A more preferablerange thereof is about 6 to 0, and a most preferable range thereof isabout 5 to 0. This defined range of the snarl value is preferred for asatisfactory twist set by heat treatment and to obtain a practicalcrimped yarn.

The snarl value is measured by an instrument illustrated in FIG. 1.Twisted yarn, that is, a sample subjected to a twist set by a heattreatment is hanged on hook A, pin B and hook C under a suitable load(about (0.98 to 2.94)×10⁻²N) {1 to 3 gf}, and then the sample is fixedby hook A and hook C. And a head of the load is put on a part where thesample is contacted with pin B. And then, the sample is removed from thepin B, and snarl stops at a position. This position is measured ondivisions of the instrument. A figure measured on the divisions isdefined as an index of snarl value. This measurement is repeated thirtytimes, and a mean of these thirty measured values is defined as thesnarl value (significant figure is a decimal first place). That is, thesnarl value is measured according to JIS L 1095(1999) 9.17.2 B thatshows a testing method for general spun yarn.

We explain a treatment with steam having high temperature and highpressure mentioned above more concretely by using FIG. 3. But anembodiment mentioned below is one of embodiments of the presentinvention, so the present invention is not limited to this embodiment.

A device of the present invention shown in FIG. 3 contains autoclave 31,which can be sealed, and in which cheese yarn 32 of a heat-resistanthigh functional fiber primarily twisted can be loaded. In FIG. 3, symbol33 is a vacuum pump, which through a pipe 34 for reducing pressure,through exhausting pipe 35 and through the vacuum pump 33, is connectedwith the autoclave 31. Symbol 36 is a pipe for providing steam havinghigh temperature and high pressure or water having high temperature andhigh pressure, which through operation valve 37 is connected with theautoclave 31.

And, in the device of the present invention, the autoclave 31 isequipped with a pressure gage 38, a thermometer 39, a safety valve 40, apressure sensor 41 and a temperature sensor 42.

Moreover, a draining pipe 43 for draining water from the autoclave 31after treatment with steam having high temperature and high pressure,and the exhausting pipe 35 for returning the pressure in the autoclaveto atmospheric pressure are connected with the autoclave 31 mentionedabove. The pipe for reducing pressure 34, the exhausting pipe 35 and thedraining pipe 43 are equipped with manual operation valves 44, 45, and46, respectively.

For example, treatment with steam having high temperature and highpressure can be performed by using the above device as follows. First,the yarn cheese 32 is loaded into the autoclave 31, the manual operationvalve 44 of the pipe for reducing pressure 34 is opened, and the manualoperation valve 45 of the exhausting pipe 35 and the manual operationvalve 46 of the draining pipe 43 are closed after the vacuum pump 33begins to work. As a result, air in the autoclave 31 is exhausted, andpressure in the autoclave 31 is reduced to a pressure from 5.0×10³ Pa to5.0×10⁴ Pa.

Next, the manual operation valve 44 of the pipe for reducing pressure 34is closed, and the automatic operation valve 37 of the providing pipe 36is opened. And then, steam having high temperature and high pressure issupplied into the autoclave 31. Pressure and temperature are measured bythe pressure sensor 41 and temperature sensor 42, respectively, tomaintain a temperature of the steam supplied into the autoclave 31 in arange of about 130 to 250° C. for about 0.5 to 100 minutes. A controldevice 47 controls opening and closing of the automatic operation valve37 of the providing pipe 36 on a basis of the above measured values.

Herein, the above control may be peformed either on a basis of pressureor on a basis of temperature. But, preferably the above control isperformed on the basis of pressure because precision of control on thebasis of pressure is better than on the basis of temperature. And, themanual operation valves 44, 45, and 46 can be opened and closed not onlymanually, but also these valves can be opened and closed automaticallyunder control of a program, by modification to automatic operationvalves.

After treatment with steam having high temperature and high pressure,the automatic operation valve 37 of the providing pipe 36 and the manualoperation valve 44 of the pipe 34 for reducing pressure are closed, andthen the autoclave is exhausted through the exhausting pipe 35, and isdrained through the draining pipe 43. After returning the pressure inthe autoclave to atmospheric pressure in that way, the yarn cheese orthe yarn corn are removed from the autoclave 31.

After being treated with steam having high temperature and highpressure, the twisted yarn is untwisted by again twisting it in thedirection opposite to the primary twisting. For this untwisting step,used is any per-se known twisting machine, as in the primary twistingstep. At this time, yarn is so untwisted that preferably a count oftwist of the yarn is almost zero. Concretely, although the count oftwist after being untwisted is not indiscriminately defined, asdepending on fineness of yarn, the count of twist is preferably about0±100 (t/m), more preferably about 0±50 (t/m). Especially, it is morepreferable that yarn is untwisted as far it was twisted in the oppositedirection over zero. Concretely, it is more preferable that the count oftwist of untwisted yarn is about 0 to (−50)(t/m).

In this way, heat-resistant crimped yarn of the invention can beproduced. An elongation percentage during stretching of theheat-resistant crimped yarn produced by the present method is not lessthan about 6%, preferably about 10 to 50%. A stretch modulus ofelasticity of the heat-resistant crimped yarn is not less than about40%, preferably about 50 to 100%.

The heat-resistant crimped yarn of the present invention has excellentheat-resistance and elasticity, so that it has a wide range ofapplication. For example, a fabric with heat-resistance and elasticitycan be produced by weaving or knitting the heat-resistant crimped yarnby a per-se known method. Functional clothes with elasticity andexhibiting a good feeling when worn, which can be used for variousapplications which need heat-resistance and elasticity, can be producedby using this fabric. Examples of these clothes are thin safety gloveswith heat-resistance, fireman's clothes, racer's clothes, steel worker'sclothes and welder's clothes, for example.

EXAMPLE

The invention is described concretely with reference to the followingExamples.

Physical properties of samples prepared are measured and evaluatedaccording to methods mentioned below.

Limited Oxygen Index:

Measured according to JIS K7201 (1999) that indicates a combustion testfor polymer materials based on a limited oxygen index.

Thermal Decomposition Point:

Measured according to JIS K7120 (1987) that indicates a method formeasuring a thermal weight loss of plastics.

Elasticity:

Measured according to JIS L1013 (1999) that indicates a method fortesting filament yarn of chemical fibers. According to Test Method,Article 8.11.A, an elongation percentage during stretching of eachsample is determined. Preparation before a measurement is describedbelow. A skein of the sample is wrapped up in a gauze, and subjected totreatment with warm water at 90° C., for 20 minutes, and is allowed toair-dry at room temperature.

Percentage of Elastic Recovery:

Measured according to JIS L1013 (1999) that indicates a method fortesting filament yarn of chemical fibers. According to Test Method,Article 8.12, a percentage of elastic recovery of each sample isdetermined. Preparation before this measurement is described below. Askein of the sample is wrapped in a gauze, and subjected to treatmentwith warm water at 90° C., for 20 minutes, and is allowed to air-dry atroom temperature.

Fineness:

Measured according to JIS L1013 (1999) that indicates a method fortesting a filament yarn of chemical fibers. According to Test Method,Article 8.3, fineness based on a corrected weight of each sample isdetermined.

Tensile Strength:

Measured according to JIS L1013 (1999) that indicates a method fortesting filament yarn of chemical fibers. According to Test Method,Article 8.5.1, tensile strength of each sample is determined. In orderto prevent monofilaments in each sample from being disordered and togive a uniform tension to all constituent monofilaments, the sample istwisted to a twist parameter, K of 1000, before being tested.

Snarl Value:

Measured according to JIS L1095 (1999) that indicates a method fortesting ordinary spun yarn. According to Test Method, Article 9.17.2.B,a snarl value of each sample is determined.

Examples 1 to 4, and Comparative Examples 1, 2

Used was polyparaphenylene-terephthalamide filament yarn (Toray-DuPont'sCommercial product named Kevlar®) having a limited oxygen index of 29, athermal decomposition point of 537° C., a tensile strength of 2.03N/tex,and a tensile modulus of 49.9N/tex. This is composed of 131monofilaments with a fineness of 0.17 tex per filament whose totalfineness is 22.2 tex. The yarn was first twisted to a twist parameter Kof 1937 to 9909 by double twister. And a snarl value of this obtainedtwisted yarn was measured. Next, 200 g of the twisted yarn was woundaround an aluminum bobbin, and a yarn cheese was formed. And then theyarn cheese was subjected to heat-set with saturated steam at 200° C.for 15 minutes. And a snarl value of this obtained heat-set yarn wasmeasured. Next, using the same double twister, the yarn was againtwisted in the direction opposite to a primary twisting direction to acount of twist zero, whereby a heat-resistant crimped yarn of theinvention was obtained. Physical properties of the crimped yarn weremeasured. Results are shown in Table 1.

Example 5

Used was polyparaphenylene-terephthalamide filament yarn (Toray-DuPont'sCommercial product) of which fineness is 44.4 tex. The yarn was twisted,heat-set with saturated steam or through dry heat treatment, anduntwisted in the same manner as in Example 1, except that the twistparameter during a primary twisting step was 7536. Physical propertiesof this heat-resistant crimped yarn were measured. Results are shown inTable 1.

Comparative Example 3

The same yarn as in Example 1 was twisted, heat-set with saturated steamor through dry heat treatment, and untwisted in the same manner as inExample 3, except that heat-setting was performed at low temperature;that is, this twisted yarn was heat-set with saturated steam at 120° C.for 15 minutes. Physical properties of this heat-resistant crimped yarnwere measured. Results are shown in Table 1.

TABLE 1 Temperature Elongation Count of Twist of Snarl value Snarl valuePercentage Fineness Twists Parameter heat-setting before after inStretch (tex) (turns/m) (K) (° C.) heat-setting heat-setting (%) Example1 22.2 1080 5087 200 9.5 4 7 Example 2 22.2 1338 6304 200 9.5 5 17.6Example 3 22.2 1753 8260 200 9.5 5.5 28 Example 4 22.2 2103 9909 200 9.66 31.6 Example 5 44.4 1131 7536 200 9.4 5.2 29.6 Comp. Ex. 1 22.2 4111937 200 8 2 3.5 Comp. Ex. 2 22.2 549 2587 200 9 3 4 Comp. Ex. 3 22.21753 8260 120 9.5 8.5 4.9

The twist parameter in Examples 1 to 4 was a high level, and a snarlvalue of the yarn before twist-setting was less than 9.5. The twistedyarn was twist-set by heat treatment with saturated steam. As a result,a snarl value of the yarn after twist-setting was 4 to 6, and it showedtwist was fixed. So, an elongation percentage during stretching of aheat-resistant crimped yarn obtained by untwisting the twist-set yarnwas 7 to 31.6%. This level of an elongation percentage during stretchingwas satisfactory to raw material for stretchable and excellent woven andknitted fabric. And an amount of a yarn wound around a bobbin was small,so lack of uniformity of heat-setting between a surface and an interiorof the yarn cheese was not observed.

And, in Example 5, a snarl value of the yarn after twist-setting was 4to 6, and twist was sufficiently fixed. So, an elongation percentageduring stretching of a heat-resistant crimped yarn obtained was 29.6%.The said heat-resistant crimped yarn was satisfactory to raw materialfor stretchable and excellent fabric. And an amount of the yarn woundaround a bobbin was small, so lack of uniformity of heat-setting betweena surface and an interior of the yarn cheese was not observed.

On the other hand, in Comparative Examples 1 and 2, a snarl value of theyarn after twist-setting is low, that is 2 and 3, and twist was fixed.But a twist parameter of primary twisting was low, so an elongationpercentage during stretching of a heat-resistant crimped yarn obtainedwas low, that is 3.5 and 4%. As a result, a stretchable and excellentfabric could not be obtained.

In the Comparative Example 3, a snarl value of the yarn aftertwist-setting was 8.5, and twist was not sufficiently fixed. Anelongation percentage during stretching of a heat-resistant crimped yarnobtained was 4.9, so the heat-resistant crimped yarn was notsatisfactory for raw material for stretchable and excellent fabric.

Example 6

Used was polyparaphenylene-terephthalamide filament yarn (Toray-DuPont'sCommercial product named Kevlar®) having a limited oxygen index of 28, athermal decomposition point of 537° C., a tensile strength of 2.03N/tex,and a tensile modulus of 49.9N/tex. And its fineness was 22.2 tex. Theyarn was first twisted to a twist parameter K of 7539 by a doubletwister. And 1 kg of this twisted yarn was wound around an aluminumbobbin, around which 1 kg yarn could be wound, and a yarn cheese wasformed. In the yarn cheese, an internal diameter of a bobbin cylinderwas 84 mm, an external diameter of a bobbin cylinder was 90 mm, a widthof the yarn cheese was 164 mm, a thickness thereof was 25 mm and awinding density thereof was 0.7 g/cm³.

The above bobbin was loaded into an autoclave, and pressure in theautoclave was reduced to 2.7×10⁴ Pa for three minutes. Later, saturatedsteam at 180° C. was provided in the autoclave for 10 minutes. Theautoclave was left as it was for 30 minutes, steam in the autoclave wasexhausted, the pressure in the autoclave returned to atmosphericpressure, and the yarn cheese was removed.

Next, using the same double twister, the yarn was again twisted in adirection opposite to a primary twist direction to a count of twistzero, whereby a heat-resistant crimped yarn of the invention wasobtained.

A sample for testing was taken from a most-outer part, a central partand a most-inner part of the yarn cheese at heat-setting. Physicalproperties of this heat-resistant crimped yarn were measured. Resultsare shown in Table 2. A snarl value was measured after heat-set andbefore untwisting, and other physical properties were measured afteruntwisting.

Comparative Example 4

A heat-resistant crimped yarn was produced in the same manner as inExample 6, except pressure was not reduced before treatment with steamhaving high temperature and high pressure in an autoclave. A sample fortesting was taken from a most-outer part, a central part and amost-inner part of a yarn cheese at heat-setting. Physical properties ofthis heat-resistant crimped yarn were measured. Results are shown inTable 2.

Example 7

A heat-resistant crimped yarn of the present invention was produced inthe same manner as in Example 6, except that 3 kg of twisted yarn waswound around an aluminum bobbin, around which 3 kg yarn can be wound. Ina yarn cheese, an internal diameter of a bobbin cylinder was 64 mm, anexternal diameter of a bobbin cylinder was 70 mm, a width of the yarncheese was 170 mm, a thickness thereof was 60 mm and a winding densitythereof was 0.7 g/cm³.

A sample for testing was taken from a most-outer part, a central partand a most-inner part of the yarn cheese at heat-setting. Physicalproperties of this heat-resistant crimped yarn were measured. Resultsare shown in Table 2.

Example 8

A heat-resistant crimped yarn of the present invention was produced inthe same manner as in Example 6, except that saturated steam at 200° C.was provided in an autoclave for 10 minutes, and the autoclave was leftas it was for 15 minutes, A sample for testing was taken from amost-outer part, a central part and a most-inner part of a yarn cheeseat heat-setting. Physical properties of this crimped yarn were measured.Results are shown in Table 2.

TABLE 2 Elongation Percentage Snarl Tenacity in Stretch Part Value(N/tex) (%) Example 6 Most-outer 4.9 1.39 29.4 Central 5.0 1.37 29.1Most-inner 4.7 1.37 28.9 Comparative Most-outer 4.9 1.38 29.7 Example 4Central 6.9 1.42 20.2 Most-inner 8.1 1.46 4.8 Example 7 Most-outer 4.81.38 29.8 Central 4.6 1.37 30.1 Most-inner 4.9 1.38 29.6 Example 8Most-outer 4.3 1.35 30.5 Central 4.7 1.36 31.5 Most-inner 4.5 1.34 31.0

As it is shown in Table 2, in Examples 6 to 8, there is no difference inthe physical properties of a heat-resistant crimped yarn of theinvention between the most-outer part and the most-inner part of theyarn cheese. On the other hand, in Comparative Example 4, an elongationpercentage during stretching in the most-inner part is lower than thatin the most-outer part of the yarn cheese, and there was lack ofuniformity of heat-setting between the surface and the interior of theyarn cheese. An elongation percentage during stretching is mostimportant for a heat-resistant crimped yarn.

Example 9

Small round through holes, of which diameter is 4 mm, were madeuniformly on a surface of a heat-resistant bobbin made of aluminum,wherein an internal diameter of a bobbin cylinder was 84 mm, an externaldiameter of the bobbin cylinder was 90 mm, and a width of yarn cheesewas 164 mm. A number of the through holes was 96, and concretely was 8in a vertical direction and was 12 in a circumferential direction. Inthis case, a hole area rate was 2.7%.

Used was polyparaphenylene-terephthalamide filament yarn (Toray-DuPont'sCommercial product named Kevlar®) having a limited oxygen index of 28, athermal decomposition point of 537° C., a tensile strength of 2.03N/tex,and a tensile modulus of 49.9N/tex. And its fineness was 22.2 tex. Theyarn was first twisted to a twist parameter K of 7539 by a doubletwister. And this twisted yarn was wound around the bobbin describedabove, and a yarn cheese was formed. A width of the yarn cheese was 25mm and a winding density thereof was 0.7 g/cm³.

The above yarn cheese was loaded into an autoclave. Heat treatment withsaturated steam at 180° C. was performed for 30 minutes.

Next, using the same double twister, the yarn was again twisted in adirection opposite to a primary twisting direction to a count of twistzero, whereby a heat-resistant crimped yarn of the invention wasobtained.

Comparative Example 5

A heat-resistant crimped yarn was produced in the same manner as inExample 9, except that the number of the through holes is different, andthe hole area rate is small, that is 0.97%. The number of the throughholes was 32, and concretely was 8 in a vertical direction of a bobbinand was 4 in a circumferential direction of the bobbin. In this case,the through holes are small and round, of which diameter is 4 mm.

A sample for testing was taken from a most-outer part, a central partand a most-inner part of a yarn cheese at heat-setting. Physicalproperties of this crimped yarn were measured.

Comparative Example 6

A heat-resistant crimped yarn was produced in the same manner as inExample 9, except that the number and size of the through holes aredifferent. The number thereof was 40, and concretely was 8 in a verticaldirection of a bobbin and was 5 in a circumferential direction of thebobbin. And the size of the through holes was big, that is, a diameterthereof was 10 mm.

Comparative Example 7

A heat-resistant crimped yarn was produced in the same manner as inExample 9, except that the number and size of the through holes aredifferent. The number thereof was 1482, and concretely was 26 in avertical direction of a bobbin and was 57 in a circumferential directionof the bobbin. And the size of the through holes was small, that is, adiameter thereof was 1 mm.

Results are shown in Table 3. A snarl value was measured afterheat-setting with steam having high temperature and high pressure andbefore untwisting, and an elongation percentage during stretching and apercentage of elastic recovery were measured after untwisting.

TABLE 3 Comparative Comparative Comparative Example 9 Example 5 Example6 Example 7 Diameter of the through hole 4 4 10 1 (mm) Number of thethrough hole 96 32 40 1482 (that in the vertical direction × (8 × 12) (8× 4) (8 × 5) (26 × 57) that in the circumference direction) Hole arearate (%) 2.67 0.97 5.38 2.00 Snarl value Most-outer part 4.8 4.8 4.7 4.8Central part 4.6 6.8 4.8 4.7 Most-inner part 4.7 7.2 4.9 4.7 ElongationMost-outer part 30.0 30.5 percentage Central part 29.5 18.3 in stretch(%) Most-inner part 29.6 4.5 Percentage of Most-outer part 7.4 7.4elastic Central part 7.3 4.5 recovery (%) Most-inner part 7.4 0.5

From data of Example 9 and Comparative Example 6, the hole area rate ispreferably not less than 1% in order to perform a satisfactory heat-setof the yarn cheese. In Example 9, the hole area rate of the bobbincylinder was 2.67%, and steam was infiltrated into a most-inner part ofthe yarn cheese. So, all twists, from a most-outer part to themost-inner part of the yarn cheese, were fixed uniformly as a snarlvalue showed. As a result, an elongation percentage during stretchingand a recovery percentage of elasticity of a heat-resistant crimped yarnobtained by untwisting were uniform all over the yarn cheese, from themost-outer part to the most-inner part. Herein, an elongation percentageduring stretching is indicative of elasticity, and a recovery percentageof elasticity is indicative of contractibility. On the other hand, inComparative Example 5, the hole area rate of the cylinder of the bobbinwas 0.97%, and steam did not infiltrate into a most-inner part of theyarn cheese efficiently. So a snarl value of the yarn in the most-innerpart is high, and in heat-resistant crimped yarn obtained by untwisting,an elongation percentage during stretching and a recovery percentage ofelasticity of the yarn in the most-inner part were quite worse than inthe most-outer part of the yarn cheese.

And in Comparative Example 5, marks of the through holes were made on aheat-resistant crimped yarn. Thus, the diameter of the through holes ispreferably less than 9 mm so as not to make marks on a heat-resistantcrimped yarn.

In Comparative Example 5, the through holes were blocked with fiberdeposit (waste fiber). That is, during a twisting process, filaments ofthe yarn touch a yarn guide and are worn down. As a result, fibril (finenap) is released, and that released fibril gets deposited, (wastefiber). A kind of surfactant, which prevents fibers from generation ofstatic electricity, and those fibers deposited adhere to inside of thethrough holes, therefore, the through holes were clogged. Accordingly,the diameter of the through holes is preferably more than about 2 mm toperform treatment with steam having high temperature and high pressurewithout clogging up the through holes.

INDUSTRIAL APPLICABILITY

This invention is characterized by a method for producing aheat-resistant crimped yarn comprising: primary twisting yarn of aheat-resistant high functional fiber; twist-setting this twisted yarn byheat treatment; and untwisting this twist-set yarn, wherein a snarlvalue of the twist-set yarn is not more than 6.5. In this productionmethod, for example, the yarn can be sufficiently crimped by use of anyordinary autoclave or the like, in which the twisted yarn to be heat-setmay be kept at a predetermined temperature only for a short period oftime. Therefore, the production method has such advantages as anavailability of ordinary equipment, easy process control, lower costsand high productivity. By using the production method, obtained is aheat-resistant crimped yarn, with a good stretch modulus of elasticity,heat-resistance, strength and a good appearance. Since the heat-settingtreatment in the method is effected at a temperature lower than adecomposition point of a heat-resistant high functional fiber, the yarnis prevented from being deteriorated under heat. Accordingly, anexcellent and practical heat-resistant crimped yarn, which has a goodstretch modulus of elasticity and heat-resistance, can be obtained. Andthen, by using this heat-resistant crimped yarn, a fabric, which has agood elasticity and heat-resistance, can be produced. And then, by usingthis fabric, functional clothes, which have good elasticity and exhibita comfortable feeling when worn, can be produced.

And, in the method for producing a heat-resistant crimped yarn of thepresent invention, uniformity of heat-setting between a surface and aninterior of a yarn cheese by steam having high temperature and highpressure can be improved by reducing pressure in the autoclave or usinga heat-resistant bobbin which has small through holes. Therefore, byusing the present method, a heat-resistant crimped yarn mentioned abovecan be produced efficiently and on a commercial basis. A time oftreatment with steam having high temperature and high pressure isreduced by the improvement mentioned above. Accordingly, the yarn isprevented from being deteriorated under heat, therefore, aheat-resistant crimped yarn, which has a good stretch modulus ofelasticity and heat-resistance, can be obtained. Moreover, a largeamount of yarn can be crimped at a time, so production costs can bereduced, and productivity can be high.

1. A method for producing a heat-resistant crimped yarn, comprising:providing twisted yarn by twisting yarn of a heat-resistant highfunctional fiber such that said heat-resistant high functional fiber istwisted to a twist parameter K of from 5,000 to 11,000, wherein K isrepresented by the formulaK=t×D ^(1/2) with t indicating a count of twist of the fiber in terms ofturns/m, and D indicating a fineness of the fiber in terms of tex;making yarn cheese or yarn corn having a thickness of at least 15 mm andhaving a winding density of at least 0.5 g/cm³ by winding said twistedyarn around a heat-resistant bobbin having through holes in a surface ofa cylinder and/or a flange of said bobbin, with a diameter of each ofsaid through holes being from 2 mm to 9 mm, and with a hole area ratedefined by said through holes being 1% to 20%; loading said yarn cheeseor yarn corn into an autoclave; reducing pressure in said autoclave soas to be within a range of from 5.0×10³ Pa to 5.0×10⁴ Pa; bringing saidyarn cheese or yarn corn, while in said autoclave, into contact withsteam having a high pressure and a high temperature within a range offrom 130° C. to 250° C. or water having a high pressure and a hightemperature within a range of from 130° C. to 250° C., thereby providingtwist-set yarn having a snarl value of at most 6.5; and untwisting saidtwist-set yarn.
 2. The method according to claim 1, wherein twistingyarn of a heat-resistant high functional fiber comprises twisting yarnof a heat-resistant high functional fiber exhibiting an elongationpercentage of at least 6% during stretching thereof.
 3. The methodaccording to claims 2, wherein bringing said yarn cheese or yarn corninto contact with the steam having the high pressure and the temperaturewithin the range of from 130° C. to 250° C. or the water having the highpressure and the temperature within the range of from 130° C. to 250° C.comprises bringing said yarn cheese or yarn corn into such contact for aperiod of time ranging from 0.5 minutes to 100 minutes.
 4. The methodaccording to claim 2, wherein twisting yarn of a heat-resistant highfunctional fiber comprises twisting yarn of a heat-resistant highfunctional fiber selected from the group consisting of a para-aramidfiber, a meta-aramid fiber, a wholly aromatic polyester fiber and apolyparaphenylene-benzobisoxazole fiber.
 5. The method according toclaim 4, wherein the para-aramid fiber ispolyparaphenylene-terephthalamide fiber.
 6. A heat-resistant crimpedyarn produced by the method of claim
 2. 7. A fabric made fromheat-resistant crimped yarn produced by the method of claim
 2. 8. Anarticle of clothing made from fabric made from heat-resistant crimpedyarn produced by the method of claim 2.